Underwater wellhead



April 1968 J. R. LEONARD ETAL 3,378,067

UNDERWATER WELLHEAD Filed May 20, 1966 3 Sheets-Sheet 1 FIG. i

JOHN R. LEONARD JAMES W. TERRY lNVENTOR avaj p ATTORNEY April 1968 J. R.LEONARD ETAL. 3,378,067

UNDERWATER WELLHEAD 3 Sheets$heet 2 Filed May 20. 1966 JOHN R. LEONARDJAMES W. TERRY INVENTOR BY LZQW1 x9 pam/ ATTORNEY April 1968 J. R.LEONARD ETAL 3,378,067

UNDERWATER WELLHEAD Filed May 20, 1966 5 Sheets-Sheet 3 JOHN R. LEONARDJAMES W. TERRY INVENTOR BY a fi ATTORNEY United States Patent 3,378,067UNDERWATER WELLHEAD John R. Leonard, Houston, Tex., and James W. Terry,Whittier, Caiifi, assignors to Mobil Oil Corporation, a corporation ofNew York Filed May 20, 1966, Ser. No. 552,386 9 Claims. (Cl 166-.5)

This invention relates to a method and apparatus for completing asubaqueous well beneath the surface of a body of water so that thewellhead thereof can be raised to the surface for maintenance and repairoperations, and more particularly, to a flexible conductor pipe betweenthe subaqueous wellbore and the production wellhead.

Heretofore, when a subaqueous well is proven and is to be placed onproduction, as for example in the Gulf of Mexico, usually anabove-surface, bottom-supported platform is set over the well, with ariser or conductor pipe extending from the wellbore to tht platformdeck, and a christmas tree (production wellhead) is mounted atop theriser pipe on the deck above the surface of the body of Water. A numberof directional Wells can then be drilled from the deck of the platform.When the field is too shallow for directional wells, separate, spacedwells are drilled and a rudimentary support structure is constructed atthe riser pipe of each well to permit an abovesurface wellhead. Largeships must thread their way between these structures, and utmost caremust be taken, particularly during foggy weather conditions. Signallights and other warning devices must be connected to all of theplatforms and the well riser supports. However, as the more prolificproducing areas become fully developed and the number of above-surfacestructures increases, the problems of navigation, and the resultantdanger to the above-surface structures from collisions with ships,become increasingly great. While the spacing of these platform's mightnot appear to present a navigational hazard, at first glance, they dopresent one to a ships captain who is usually confronted with navigatingthrough large open areas with few obstacles. In the Gulf of Mexico wherethe density of offshore platforms is increasing at a rapid rate, therehave already been several collisions.

Another problem that should be considered in conjunction withabove-surface completions is that of the violent storms that ravage theGulf Coast with almost yearly frequency. These storms take their toll ofany equipment which is above the surface of the Water. A largeproduction platform, if uprooted, is a tremendous economic loss, anddepending upon the individual case, ten or more wells may have to beabandoned. Even the loss of a single Well can have a serious effect onthe economics of a companys offshore operations.

Therefore, it would appear to be advantageous to shelter at least theproduction wellheads beneath the surface; however, other problems arisewhen a wellhead is sheltered beneath the surface of a body of water. Oneof the most important of these is that of servicing and maintaining thewell. A diver may be used for actuating the various valves and repairingany malfunctions of the wellhead; but, even in shallow water a diverseffectiveness is less than that of a man working under atmosphericconditions and moreover he is limited at this time to working in waterof several hundred feet in depth.

While robotic and TFL (through fiowline) tools have been developed andare available for routine servicing or workover operations, thesedevices are complicated and expensive and are, at this time, only usedfor a few limited tasks. For production purposes, it is desirable tocomplete a well so that certain servicing, repair, and workoveroperations, not as easily accomplished by remote control equipment, canbe handled under atmospheric conditions. With the newly developedcapabilities of the oil com- "ice panies to drill and produce oil wellsin the waters of the continental shelf over two hundred fifty feet, andthe expected later extension of these capabilities to the continentalslope, where the depths encountered range from six hundred to twothousand feet, the need for a diver, at this time, for routine repairs,maintenance, or workover operations, must be dispensed with.

Therefore, it is an object of this invention to provide a submergedwellhead that can be brought to the surface of a body of water forrepair, maintenance, and workover operations.

Another object of this invention is to provide an improved means forremotely controlling the raising of a submerged apparatus to the surfaceof a body of Water, the apparatus having been positioned a substantialdistance beneath the surface.

Other objects and advantages of this invention will be apparent from thefollowing description taken with reference to the accompanying drawings,wherein is shown pre ferred embodiments of the invention:

FIGURE 1 is a pictorial representation of a christmas tree mounted onthe upper end of a well conductor pipe being supported in deep Water bya tripod structure and having a flexible pipe section between the tripodsupport structure and the Wellhead;

FIGURE 2 is a cross-sectional view of the flexible section of the wellconductor pipe shown in FIGURE 1;

FIGURE 3 is an elevational view, partly in cross section, showing aremotely controlled buoy of the present invention connected to asubaqueous wellhead and used as a locating marker therefor; and

FIGURE 4 is a side elevational view of a shallow water installation inwhich the christmas tree is mounted on the upper end of a well conductorpipe projecting only from the marine bottom. The conductor pipe has aflexible section permitting it to be bent over so that the christmastree rests near the marine bottom and is spaced therefrom by theperiphery of a buoy mounted on the upper end of the conductor pipe.

Referring now to the drawings, more in detail, by character reference,there is shown in FIGURE 1 conductor pipe 10 protruding from thesubaque-o-us marine bottom 12 and terminating just below a designateddistance a beeath the surface 14 of the body of water. The distance aindicates a sheltered depth at which apparatus will not be substantiallysubject to surface conditions. As to this sheltered depth at which thewave and tidal actions and surface storms would no longer be asubstantial problem, this would vary with the 'total depth of the water.A figure used with present subsurface completions off California is onehundred feet. Of course, in the shallow waters of the Gulf Coasttwenty-five to fifty feet might be more appropriate.

The conductor pipe 10 is illustrated as capped by a production wellheador christmas tree 16, shown schematically, and is braced by a tripodsupport structure 18 set on the marine bottom 12. The rigid conductorpipe section 20, below the support structure 18 is identical toconductor pipes or surface casings that are normally utilized inoffshore installations. Connected to the upper end of the rigidconductor pipe section 20, above the support 18, is a flexible conductorpipe section 22 with a rigid upper conductor pipe section 24 connectedto its free end. The upper rigid conductor pipe section 24 in turnterminates in the christmas tree 16 from which extends a fiow orshipping line 26 for carrying the production products from a subaqueouswell (not shown) to separator or storage facilities (not shown)on-shore, on the marine bottom, or on an above-surface platform. Thefiowline 26, originating at the christmas tree 16, has a flexibleportion between the christmas tree 26 and the upper end of the supportstructure 18; a rigid portion, preferably of a high strength material,such as steel pipe, paralleling the conductor pipe down to the marinebottom 12; and a flexible portion laying along the marine bottom 12. Theportion of the flowline 26 paralleling the conductor pipe would besupported by the conductor pipe 10 at intervals.

Fixed to the upper end of the support structure 18 is an invertedconical framework 28 terminating in a large diameter tubular rim 30 forabutting the rigid conductor pipe section 24 and supporting thechristmas tree 16 regardless of the direction in which the flexibleconductor pipe section 22 bends as the conductor pipe 10 is loweredbeneath the surface 14 of an offshore body of water. Also connected tothe conductor pipe 10 is a buoy 32 having a sonar-controlled variablebuoyancy. The buoy 32 is attached to the conductor pipe 10 by a cable 34fastened at its ends to padeyes 36 spaced along the length of theconductor pipe 10 above the upper end of the support structure 18 andslidably strung through a padeye 38 fixed to the lower end of the buoy32.

The construction of the flexible section 22 is shown in more detail inFIGURE 2. The flexible section 22 consists of a plurality of fluidtightball joints 40 (representatively denoted) bolted together, and to therigid conductor pipe sections 20 and 24 by end flanges 42 to form asflexible a section 22 as necessary. Each of the ball joints 40 consistsof an inner spherical shell 44 which has diametrically opposed circularopenings 46 and 48 formed therethrough. The smaller circular opening 46is extended by a tubular portion 50 integrally connected to thespherical shell 44 and having an end flange 42 fixed thereto. An outerpartially spherical shell 52, less than a hemisphere in extent, andterminating in a planar rim 54, slidably mates with the inner sphericalshell 44 over the larger circular opening 48. The partially sphericalshell 52 has a tubular portion 56 extending therefrom coincident with acentral circular opening 58 equal in size to the smaller opening 46 ofthe spherical shell 44, the tubular portion 56 also having an end flange42. An annular element 60, having an inner diameter of less than theouter diameter of the spherical shell 44, is mounted thereon oppositethe rim 54 of the partially spherical shell 52. A packing 62 is includedin the space between the annular element and the rim 54. Bolting theannular element 60 and the outer shell 52 together by means of aplurality of equally spa'ced bolts 64 causes a fluidtight seal betweenthe spherical shells 44 and 52 and the packing 62, while permitting alimited universal movement therebetween. Although the allowable degreeof movement of each of the joints 40 may be varied, it has been foundthat 20 is a good engineering compromise. If a 90 bend is desired, fivejoints 40 will be required.

Production tubing is set within the conductor pipe 10 and consists inpart of a flexible section coincident with the flexible section 22 ofthe conductor pipe 10, made up of tubular elements 66 interconnected byfluidtight flexible joints 68 which may be identical in type, althoughsmaller in size than the ball joints 40. A lower rigid section 70 of theproduction tubing, projecting out of the subaqueous well beneath themarine bottom 12, would be identical to that found in prior art wells.An upper rigid production tubing section 72 is fixed to the outermostflexible joint 68 and in operatively connected into the christmas tree16.

It can be seen in (FIGURE 1) that the conductor pipe 10 and the includedproduction tubing are arranged to be bent over into a position in whichthe christmas tree 16 rests on the rim 30 a safe distance beneath thesurface 14. In such a position, the subsea installation would not be anavigational hazard and would be protected from surface conditions, suchas wind, waves, and violent storms. The weight of the vchristmas tree 16and the upper rigid conductor pipe section 20 is alone enough to causethe conductor pipe 10 to bend into the sheltered position. In reasonablycalm water the conductor pipe 10 will hold this position until raised.Any movement of the upper end of the conductor pipe 10 caused byshifting currents and tides will not affect the depth at which thechristmas tree 16 rests due to the circular configuration of the rim 30.

To raise the christmas tree 16 ba'ck to the surface 14 for repair orworkover operations, the buoy 3.2 is activated by a sonar signal,causing it to fill with gas and thereby expelling the water therefrom(as will be explained). The buoyancy of the buoy 32 carries it towardthe surface 14 trailing the conductor pipe 10 along by means of thecable 34. The buoy 32 may be designed to bring the christmas tree 16completely out of the water or it may only rise enough so that the buoy32 itself shows on the surface. In the latter case a barge or derricknearby would be used to haul in the cable 34 until the christmas tree 16has reached the desired position above the surface 14 of the water.

In FIGURE 3 the buoy 32 is shown floating on the surface 14 of a body ofwater and connected to a permanently submerged christmas tree 16 of asubaqueous well by a cable 34. Although in this view it is shown merelyas a marker (which would be another use for such a buoy), it would be ofthe same construction as that illustrated in FIGURE 1, although smaller.At 32' the same buoy, resting on the bottom, is shown in expandedcrosssection (at the right). The cable 34' is stored on the oceansbottom until it is needed and the chance of this cable being broken, orthe buoy damaged during severe storms, as is possible if a continuouslyfloating buoy is utilized, is reasonably overcome. The buoy 32' consistsof a hollow shell 74 having a ballast section 76 therein. The ballastsection 76 is designed to hold the buoy 32' firmly to the marine bottom12, as well as to insure proper alignment of a sonar antenna 78. A checkvalve 80, biased closed, is fitted in the shell 74 of the buoy 32 topermit the expelling of the water therefrom due to internal pressure.The water is expelled by means of high pressure gas, in this casenitrogen, carried in a capsule 82 within a dome 84 on the shell 74 ofthe buoy 32'. An actuator 86 is operatively connected to the sonarantenna 78, and by conventional means, will release the nitrogen gasfrom the capsule 82 on command. Such a release means could be anexplosively driven pin that would puncture the nitrogen capsule topermit the gas to escape therefrom or a battery-operated solenoid thatwould unscrew a cap from the capsule. Such actuators are well known, andit is not believed necessary to discuss the details of such a device. Aplug 88 is threaded into one end of the shell 74. By moving this plug88, gas pressure can be released and the buoy 32' reflooded.

Now referring to FIGURE 4, the invention is shown as it would beutilized infairly shallow water of approximately one hundred feet orless. The depth at which a supplementary support structure is notnecessary is determined by a number of factors including the length ofconductor pipe that a buoy could lift to the surface. The lower rigidconductor pipe section 20 extends only a short distance up from themarine bottom 12, supported in a landing base 90, above which it iscontinued as a flexible section 22. The flexible section 22 of theconductor pipe 10 as in FIGURE 1 terminates in an upper rigid conductorpipe section 24 which is capped by a christmas tree 16. The flexiblesection 22 would be of the same length as that shown in FIGURE 1, thelength being determined only by the amount of bending required.

A second embodiment of the buoy is shown which in-- corporates thefeature of spacing the .christmas tree 16 from the marine bottom 12. Thebuoy, generally designated 92, mounted directly on the conductor pipesection 24, has a large diameter ring-shaped element forming a hollowtoroidal shell 94 supported on the conductor pipe section 24 by arigidly fixed inner sleeve or hub 96 and a plurality of interconnectingradial spokes 98. The toroidal shell 94 serves the double functions of avariably buoyant compartment and a spacer to keep the christmas tree 16away from the marine bottom 12 regardless of what direction theconductor pipe has been bent. The design of the spacer-buoy 92 can bevaried, within the concept of the invention, by enlarging the dimensionsof the hub 96 and constricting the toroidal diameter of the shell 94,the hub having the hollow compartment and functioning as the buoy whilethe other shell is only a spacer ring. However, as envisioned, as thepreferred embodiment, the toroidal shell 94 would be the hollowcompartment and would be large enough to act as a floating base tosupport the christmas tree 16 straight up out of the water when it isactuated.

Although no dome 84, carrying the sonar antenna 78, the nitrogen capsule82, and the actuator 86, is illustrated in this view, one would benecessary if the buoy is to be remotely actuated. The dome 84 could bemounted on the toroidal shell 94 or on the conductor pipe 10.

Although the present invention has been described in connection withdetails of the specific embodiment thereof, it is to be understood thatsuch details are not intended to limit the scope of the invention. Theterms and expressions employed are used in a descriptive and not alimiting sense and there is no intention of excluding such equivalentsin the invention described as fall within the scope of the claims. Nowhaving described the apparatus herein disclosed, reference should be hadto the claims which follow.

What is claimed is:

1. Apparatus for producing oil and/or gas from a subaqueous well,consisting of: a conductor pipe set in the Wellbore and protrudingtherefrom, said conductor pipe being long enough for the upper end toproject above the surface of the body of water at the well site whensaid conductor pipe is vertically positioned; a christmas tree fixed onsaid upper end of said conductor pipe and operatively connectedtherewith; means for sheltering said christmas tree beneath said surfaceof said body of water including a flexible section in said conductorpipe; production tubing within said conductor pipe for operativelyconnecting a producing zone in said subaqueous well with said christmastree for producing the fluid therethrough; and a flexible section insaid production tubing substantially coincident with said flexiblesection in said conductor pipe whereby said conductor pipe and saidincluded production tubing can be bent to shelter said christmas treebeneath said surface of said body of water, and can be verticallystraightened to project said christmas tree above said surface of saidbody of Water.

2. The oil and/or gas production apparatus as recited in claim 1 whereinsaid flexible conductor pipe consists of a plurality of spherical balljoints having a continuous passage extending therethrough, each of saidball joints having a limited degree of universal movement.

3. The oil and/or gas production apparatus as recited in claim 1 whereinthere is means for coacting with said conductor pipe between saidflexible section and said christmas tree to limit the bending of saidflexible section.

4. The oil and/or gas production apparatus as recited in claim 3 withinsaid limiting means consists of an invetted conical framework having anupper tubular rim, said conical framework being fixed, at least at itsapex, on said conductor pipe beneath said flexible section, whereby saidconductor pipe, between said flexible section and said christmas tree,abuts said tubular rim of said conical framework as the conductor pipeis bent down to be sheltered.

5. The oil and/or gas production apparatus as recited in claim 3 whereinsaid limiting means consists of a large diameter ring-shaped elementmounted on said conductor pipe between said flexible pipe section andsaid christmas tree, whereby the periphery of said ringshaped elementabuts a horizontal surface beneath said flexible section of saidconductor pipe as said conductor pipe is bent down to be sheltered.

6. The oil and/or gas production apparatus of claim 1 wherein there isremotely controlled means for straightening said conductor pipe toposition said christmas tree at least above its sheltered position.

7. The oil and/or gas production apparatus of claim 6 wherein saidremotely controlled means for straightening said conductor pipe consistsof: a variably buoyant buoy; means for attaching said buoy to saidconductor pipe; and means for remotely increasing the buoyancy of saidbuoy whereby a command signal at the surface will cause said upper endof said conductor pipe to rise toward said surface with said christmastree.

8. The oil and/or gas production apparatus of claim 7 wherein said meansfor attaching said buoy to said conductor pipe consists of: a cableconnected between axially spaced points on said conductor pipe; andmeans for slidably attaching said buoy to said cable between said spacedpoints.

9. The oil and/or gas production apparatus of claim 7 wherein there ismeans associated with said buoy for limiting the bending of saidconductor pipe and spacing said christmas tree a distance above ahorizontal surface below said limiting means consisting of a toroidallyshaped hollow compartment coaxially encircling said conductor pipe; andsaid means for attaching said buoy to said conductor pipe consists of asleeve fixed on said conductor pipe, having radial spokesinterconnecting said sleeve and said buoy.

References Cited UNITED STATES PATENTS 2,676,787 5/1954 Johnson -73,017,934 1/1962 Rhodes et al. l66.5 X 3,025,912 3/1962 Schramm et al166-46 X 3,041,090 6/1962 Ashe et a1 166-.5 X 3,055,429 9/ 1962 Tauschet a1.

CHARLES E. OCONNELL, Primary Examiner. RICHARD E. FAVREAU, AssistantExaminer.

1. APPARATUS FOR PRODUCING OIL AND/OR GAS FROM A SUBAQUEOUS WELL,CONSISTING OF: A CONDUCTOR PIPE SET IN THE WELLBORE AND PROTRUDINGTHEREFROM, SAID CONDUCTOR PIPE BEING LONG ENOUGH FOR THE UPPER END TOPROJECT ABOVE THE SURFACE OF THE BODY OF WATER AT THE WELL SITE WHENSAID CONDUCTOR PIPE IS VERTICALLY POSITIONED; A CHRISTMAS TREE FIXED ONSAID UPPER END OF SAID CONDUCTOR PIPE AND OPERATIVELY CONNECTEDTHEREWITH; MEANS FOR SHELTERING SAID CHRISTMAS TREE BENEATH SAID SURFACEOF SAID BODY OF WATER INCLUDING A FLEXIBLE SECTION IN SAID CONDUCTORPIPE; PRODUCTION TUBING WITHIN SAID CONDUCTOR PIPE FOR OPERATIVELY